For most people, summer is synonymous with happiness: vacation trips to the beach, barbecues, endless fun and adventures. However, for farmers, summer is not exactly a cause for happiness.
Yes, well, we all love being on vacation and cocktails on the beach… but no one can imagine the consequences of temperature changes that summer causes on crops.
In fact, for farmers, each of the seasonal changes (summer, autumn, winter, and spring) represents a challenge that they must know how to face intelligently to succeed and that these environmental changes do not ruin their harvest.
So, if it is already getting very hot in your greenhouse, we recommend you take a look at this article. You will learn everything you need to know about growing in a greenhouse during the summer.
What happens to crops when temperatures are high?
Before we get down to the whole issue of how high temperatures affect our greenhouse crops, it is necessary to have some basic knowledge of plant nutrition.
First of all, let’s remember that all living beings (and that includes even us, human beings) are made up of 85% water. In the case of plants, this other 15% is known in science as “dry matter”.
96% of this “dry matter” is made up of hydrogen, carbon, and oxygen that they get from the air and water, while the remaining 4% (which is just 1% of the plant’s weight ) corresponds to what we call micronutrients and macronutrients.
Subtracting a few numbers from the explanation and being a little more specific, basically, that means that the plants in our crop are “structures” full of water.
This “structure” is built around carbohydrates and other molecules that the plant synthesizes during photosynthesis and other metabolic processes. But to do so, they need both enzymes and proteins and lipids.
When it comes to nutrition, we almost always focus our attention on the crop’s fertilizer, as this is where the greatest amount of macro and micronutrients is concentrated. However, is this entirely true? Not necessarily.
The success of a crop, whether or not it is grown under greenhouse conditions, depends on how many carbohydrates the plant can produce to stimulate its growth. That is true, and we already know that. However, what many ignore is that accumulation depends not only on photosynthesis but also on respiration. This is because the carbohydrates synthesized in photosynthesis will be consumed by the respiration of plant cells.
Both processes, respiration, and photosynthesis, depends on the temperatures to which the crop is exposed, but both behave in different ways.
In the case of breathing, the increase rises with higher temperatures, but only to a certain extent. Beyond the 50ºC barrier, respiratory enzymes degrade.
On the other hand, with photosynthesis, up to just over 35ºC the temperature activates the photosynthetic process, but higher temperatures begin to inhibit it… even though we are still far from the temperature at which the enzymes are degraded.
When temperatures rise in our greenhouses during the summer, not only are our plants less able to synthesize carbohydrates, but they also consume many more of them during breathing, both day and night.
Exposed to daytime temperatures of 30ºC and nighttime temperatures of 20ºC, it is very likely that the accumulation of carbohydrates is insufficient to supply the number of fruits that the plant is trying to grow and fatten. So, as a consequence, what we want to hear the least: abortion of fruits and loss of production. Ugh.
Some tips for summer cultivation
No farmer wants to lose fruit or see his or her plants decay because of summer, we know that. However, seasonal climate change is imminent — does that mean you cannot do anything about it? Of course not!
To overcome the siege of high temperatures, here are some tips you can use to grow in greenhouses during the summer.
Provide Ventilation on Greenhouse
You should have proper ventilation and air vents installed in your greenhouse. This will let cool air pass in your greenhouse and will take out the hot air from the greenhouse. This is the most effective way to make your greenhouse cooler.
However, you should keep in mind that your ventilation should have a mesh cloth or a screen. This will protect your crops from outside bugs and insects. You don’t want those insects ending up in your greenhouse.
Choose the right crops
When heat strikes, it is very important to keep in mind that not all fruits and vegetables, no matter how good your greenhouse is, are suitable for that type of climate.
If you are thinking of using your summer vacation to start your greenhouse growing, we recommend looking for plants that are fruit-bearing and able to withstand high temperatures.
Plants with large green leaves are a very good choice, as they do well with the sun’s rays. Lettuce, for example, is one of the most widely consumed vegetables that can withstand high temperatures. Make sure you give them good hydration and partial shade and they will grow big and beautiful in less than two months.
Other good options for growing in high summer temperatures are radishes, green beans, beans, and even beets!
Give your plants some sunshade
Imagine you are going on vacation to the Caribbean with your whole family. They enjoy the beach, drink some cocktails by the sea… but the sun hits their skin all day long.
With the euphoria of the holidays, everyone forgot to bring sunscreen or rent an umbrella to protect themselves from the strong rays of the yellow giant. As a result, you woke up the next day looking not only like a shrimp, but so sore from the sunstroke that you cannot move.
Something similar happens with plants in the summer. After all, heat isn’t the only thing affecting them. Although it may not be the most glamorous option, using a cover to give partial shade to your plants is a highly effective option.
In these cases, if our crop is under a greenhouse is quite useful. If the roof of your greenhouse is made of transparent plastic, you can spread a cover over it.
What you can do is cover the Glazing Material (top of your greenhouse) with shade cloth, It will regularize the light intensity and will also help in keeping your greenhouse cool in hot summer.
However, you should keep in mind that your plants should never, under any circumstances, be in total darkness. Remember that they need enough light to perform photosynthesis. In that sense, we recommend to put the cover in the hours of the day with more intense sun and to remove it when the temperature begins to lower.
Water your plants well
We already know that this sounds like the A1 indication they give to children about plant care. However, in summer, you should consider this aspect to be extremely important. Why? Let me remind you once again who the enemy is: the heat.
To combat the high temperatures of summer, a proper irrigation pattern or system is extremely important. Not only because it refreshes your plants, but also because they are more likely to be affected by drought on summer days.
For this reason, several experts in biology and agriculture point out that during the summer, crops should be irrigated approximately twice as much. When temperatures begin to rise, these watering patterns should ideally occur with cool, warm water. Nothing too cold or too hot.
In this way, the plant will begin to cool from the roots upwards as the water circulates through the plant’s vascular system. Remember, we want to cool the crop, not drown it.
Also, you will need to start being very careful with these patterns. In summer, since temperatures will vary greatly throughout the day, you should set watering times to coincide with the less hot times of the day. I mean, during the morning or mid-afternoon.
What? Are we not supposed to support plants when it’s hotter? It certainly may seem the most logical choice, but not in this case. Why? This is because, at times when the heat is stronger, the plants will find it difficult ( due to the high humidity) to absorb as much water as possible.
In that case, what should I do when the heat is too intense and my plants are suffocating? First of all, and perhaps even more important than anything else, get ahead of events.
Take out your calendar and start looking at the weather forecast. Keep track of the days with hottest forecasts and be sure to prepare your plants for them. Slightly increase watering patterns to ensure adequate moisture levels for when those days come.
However, you will always have to make sure that the sun does not fall directly on the plants at the time of watering. This will ensure better water use.
A little extra advice about water
To make your greenhouse crops especially strong in summer, many experts recommend getting up early (more than usual ) and watering your plants early in the morning with a good dose of nutrients. This practice, on an extremely hot day, will reduce or eliminate stress.
If summer heat days still outweigh your crops after that, you may have no choice but to add an extra watering session during the day, especially if you notice that the soil is too dry.
In these cases, it is also advisable to spray the plant with water. Be careful, because if the drops that fall on the leaves are very large, they can end up burning with the effect of the sun.
Is summer in your town yet?
Do not forget that this is a space where we love to share. If you have one or more extra tricks that we have not mentioned, feel free to share them with us and other readers in the comment box. Discuss, propose, tell us your anecdotes and experiences! We want to be part of your experience as a farmer, and we want you to be part of ours.
See you in the next post!